1. Field of Invention
This invention relates generally to infusion pumping systems for medical use in intravenous therapy, and more particularly to a disposable pump set adapted to cooperate with a rotor assembly block to provide a peristaltic pump action.
In modern medical practice, patients in hospitals and in other facilities are in many cases treated for various maladies with medicaments and nutritional substances dissolved in a liquid carrier. These therapeutic solutions are infused directly into a vein or artery of the patient by a process generally designated as intravenous (IV) therapy.
The simplest embodiment of an IV infusion system takes the form of a solution container supported at an elevated position relative to the patient to be treated to provide gravity flow through a flexible pipe leading to a catheter inserted in the patient. The rate of fluid flow is set by an adjustable clamp in the fluid line, flow rate being indicated by a drip chamber just below the container. By counting the number of drops which fall during a given interval, the attendant obtains an approximate reading of flow rate.
A gravity feed IV system leaves much to be desired; for while the physician treating the patient will specify a particular solution for IV therapy and indicate the volume of solution to be administered, as well as the flow rate of infusion, it is difficult for the nurse to comply with this prescription unless she carefully monitors the gravity-feed system to be sure it is operating in the desired manner. Since a nurse has other pressing duties, she may not be able to give the system the repeated attention it demands.
To obviate the drawbacks incident to gravity-feed IV systems, it is known to employ electronically-controlled, motor-operated peristaltic pumps to feed a prescribed volume of IV solution into a patient at a carefully regulated flow rate. The clinical use of such infusion pumps is now commonplace in intensive care and special care hospital facilities for patients who require IV infusion with a degree of accuracy and reliability that cannot be realized with a gravity feed system.
When using an IV pumping system, one must exercise care to minimize the risk of air embolism. Thus, should the pump still be in operation after the container is emptied of its solution, the pump will then proceed to infuse air into the patient, and this may have serious consequences. Moreover, air, rather than solution, may be pumped into the patient should the peristaltic pump chamber included in the pump set be ruptured or separated from its fittings.
One commercially available IV infusion pump system is the "Extracorporeal" Model 2100 infusion pump manufactured by Extracorporeal Medical Specialties, Inc., of King of Prussia, Pa. The main component of this system is a solid state motordriven device for controlling the rate of flow during the administration of IV fluids. The device makes use of a rotarytype pumping action employing a single size pump chamber for all flow rates.
In the Extracorporeal system, the pumping action is effected by means of a detachable plastic rotor assembly and an independent IV pump set having integral therewith a silicon-rubber tube function as the pump chamber. This pump chamber is joined to the rotor assembly which is provided with a set of rollers, pressure between the rollers and the stator wall of the assembly acting to occlude the flexible pump chamber and thereby trap the fluid therein.
As the rotor is turned by the internal motor, the points of occlusion then advance to progressively push the fluid through the pump chamber, flow rate being controlled by adjusting the speed of the motor. Because the IV pump set is independent of the rotor assembly, it affords a sealed, sterile fluid pathway. The set is disposable after a single 24-hour use in compliance with existing medical requirements.
Another commercially-available IV system is the "Simplicity" volumetric infusion pump system manufactured by Critikon, Inc., of Tampa, Fla. The "Simplicity" system, which is generally similar in structure and function to the system marketed by Extracorporeal, also includes an independent pump set having a flexible pump chamber which cooperates with a rotor assembly to define a peristaltic pump for forcing a therapeutic fluid into the patient at a controlled rate. It further includes an alarm that is activated if the fluid container is empty, or if the tubing in the set is kinked or is dislodged from the rotor assembly.
In the "Simplicity" system, an empty bottle condition is sensed by a flow detector placed in the upper portion of the drip chamber so that it will detect the absence of fluid from the bottle while there is still fluid in the line. But no protective means are provided in this or any other commercially-available system for sensing the presence of air in the line at the outlet side of the pump chamber leading to the patient.
Thus, in practice, air may be drawn into the relatively delicate pump chamber if it is torn or punctured, or separated from its fittings. A flow detector which senses air resulting from the absence of fluid flow from the container will not give an alarm should air be entrained into the pump chamber from which it will be pumped into the patient and give rise to air embolism.
Another source of danger in an IV infusion pumping system lies in the possibility that the independent pump set which cooperates with the rotor assembly may inadvertently be installed therein in reverse; that is to say, with its outlet connector placed on the inlet side and its inlet connector placed on the outlet side of the rotor assembly. In this event, instead of infusing a therapeutic solution into the patient, blood will be drawn out of the patient. No provision is made in systems of the type heretofore known to positively preclude this possibility, which is sometimes referred to as a "Vampire" action.
Another problem heretofore experienced with systems which make use of an independent pump set is the difficulty of joining the set to the rotor assembly. While experienced personnel may be able to correctly install the set, this is not true of the more typical hospital attendant.
2. Prior Art
Systems which include motor-controlled pumps in an IV system to feed a solution intravenously in a patient are disclosed in the following patents:
______________________________________ Moulinier 2,483,924 1949 Ferrara et al. 2,102,523 1937 Lee 2,804,023 1957 Daniels 2,909,125 1959 Cantor 3,138,104 1964 Hahn 3,137,242 1964 ______________________________________
Among the patents which disclose electronic control equipment to govern the operation of the pump motor in an IV system are the following:
______________________________________ Jess et al. 4,217,993 1980 Willock 3,848,592 1974 Weishaar 3,799,702 1974 Shim 4,278,085 1981 Brown 4,256,437 1981 ______________________________________
The following patents relate tot he structure of peristaltic pumps;
______________________________________ Lepp et al. 4,142,845 1979 Casson et al. 4,184,815 1980 Spinosa et al. 3,927,955 1975 Hankinson 3,963,023 1976 ______________________________________